Quantum materials operate under the laws of quantum mechanics, where electrons occupy distinct energy states. These states form a ladder structure, with the highest level known as the Fermi energy.

Electrons, being charged particles, interact with each other in a correlated manner. The team led by Si has revealed that these interactions can lead to the emergence of new flat bands at the Fermi level, significantly impacting the material’s properties.

“Flat electronic bands near the Fermi energy have the potential to create new quantum phases and unique low-energy behaviors,” explained Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy at Rice University.

Unlike classical particles, electrons in quantum mechanics can exhibit quantum interference, resulting in flat bands where their energy remains constant regardless of changes in momentum.

The team’s findings pave the way for designing materials with flat bands, offering new avenues for applications in quantum computing, qubits, and spintronics. By linking immobile and mobile electron states through interactions, these materials can exhibit a new type of Kondo effect, enhancing their mobility.

“The unique topology of flat bands pinned to the Fermi energy opens up possibilities for realizing novel quantum states of matter,” noted Lei Chen, a Ph.D. student at Rice University.

Furthermore, the research demonstrates the potential of flat bands to host anyons and Weyl fermions, which are massless quasiparticles with electric charge. These particles could play a crucial role in developing qubits and advancing spin-based electronics.

The study also suggests that materials with flat bands could exhibit strong responsiveness to external signals, enabling advanced quantum control. This could lead to the development of topological semimetals that operate at relatively high temperatures, expanding the possibilities for practical applications.

“Our research lays the groundwork for utilizing flat bands in designing and controlling novel quantum materials that can operate at higher temperatures,” Si stated.

Contributors to this groundbreaking research include Fang Xie and Shouvik Sur, postdoctoral associates at Rice University; Haoyu Hu, a postdoctoral fellow at Donostia International Physics Center; Silke Paschen from the Vienna University of Technology; and Jennifer Cano, a theoretical physicist at Stony Brook University and the Flatiron Institute.